Shelling-resistant rail



United States Patent 2,793,947 SHELLlNG-RESIS'IANT RAIL Albert N.Swanson, Wheaton, 111., assignor to United States Steel Corporation, acorporationof New Jersey No Drawing. Application December 27, 1954,Serial No. 477,930

2 Claims. (Cl. 75-126) This invention relates to a railroad or similartrack rail and, in particular, to a rail having a greatly increasedresistance to shelling.

Railroads carrying heavy traflic over hilly terrain have considerablediificulty in track maintenance because of the early failures of railsby shelling at the gauge corners of the rail head. Shelling is theflattening of the rail head, .usually accompanied by longitudinalsplitting, resulting from the cold-working of the metal under the heavyand repeated impact of the passage of car wheels. Attempts have beenmade to avoid this difl'lculty by using a special-analysis steel for therolling of rails, e. g., 3% chromium steel, or by subjecting rails afterrolling to a special heat treatment. Both these remedies increase thecost of making rails. It is accordingly the object of my invention toprovide a rail composed of steel having only small additions of alloyingelements which will, nevertheless, have the high hardness, yield pointand tensile strength necessary to resist shelling, after normal coolingfrom the hot-rolling temperature and without any post-cooling heattreatment.

In a preferred embodiment and practice of the invention, I produce railsfrom a steel containing about the same percentage of carbon asconventional rail steel (.64.82% carbon, .601.0% manganese and .10.23%silicon) but higher in manganese and silicon and containing also a smallpercentage of chromium and a minute amount of vanadium. A rail producedfrom such steel by known methods has, when cooled in the usual mannerfrom the hot-rolling temperature, a yield point in excess of 100,000 p.s. i., a tensile strength in excess of 160,000 p. s. i., an elongationin 2" of 8-10%, a reduction in area at the fracture of 15-26% and anaverage (center and surface) Brinell hardness number from-310 to 365.These properties make it much more highly resistant to shelling thanrails of conventional rail steel.

More particularly, I provide a rail of aluminum-killed steel, having afine-grained (pearlitic) micro-structure and a composition within thefollowing ranges:

Nice

The preferred analysis is:

Percent Carbon About .70 Manganese About 1.30 Silicon About .30 ChromiumAbout 1.00 Vanadium About .12

and the balance iron with the same exceptions as given above.

A heat of such steel is made by the practice ordinarily followed inproducing fine-grained steel in the openhearth furnace. After tapping,the steel is killed by the addition of aluminum and teemed into ingotmolds. The ingots are reduced to blooms and the blooms to rails byhot-rolling in the known manner. The blooms are preferably rolled at astarting temperature of from 2150-2250 F. and the rails are finished atfrom 19002000 F. The finished rails are cooled in air on a hot bed from1900 F. to a temperature from 7001000 F. and are then subjected tocontrolled cooling in an insulated container in the known manner, to 300F. in a period of 10 or 12 hours or more.

When finally cooled, a rail produced as described above, from a steelwithin the composition ranges given, will have a fine-grained, pearliticmicro-structure and will exhibit a remarkably high resistance toshelling. The improvement in this respect is evident from the fact that,under test, the improved rail showed signs of shelling only after eightmillion contacts by a loaded wheel, compared to one million for a railof conventional steel.

Table I below gives the analyses of several examples of steels suitablefor producing rails in accordance with the invention.

Table I Heat No. 0 Mn st or v P s Cu Ni Al Table II below gives thephysical properties of the steels listed in Table I.

Table II Brinell Yield Tensil Percent Percent Heat No. Hard- Point,Strength, Elong. Redue.

ness p. s. i. p. s. i. in 2" in Area It will be apparent from theforegoing that the rail of my invention is quite hard so it endures wearwell, but is also ductile so it is not subject to early breakdown undercold-working. Taken together, these properties afford a greatlyincreased resistance to shelling under heavy loads, as compared to theperformance of ordinary carbon-steel rails. The prime advantage of myrail however, is that it attains its hardness by air cooling from thehot-rolling temperature to the intermediate temperature below whichcooling is continued at a controlled slow rate. No special post-coolingheat treatment is needed. Finally, the amounts of alloying additions 3(chromium and vanadium) are so small that they do not increase the costvery much. The improved rails, furthermore, may be made in existingmills as presently equipped.

Although I have disclosed herein the prefen'ed embodiment of myinvention, 1 intendto.cover--as welliany change or modification thereinwhich may be made Without-departing from the spirit and scopeof theinvention;

I- claim:

1. A railroad rail of-fine-grainedalloy steel consisting essentially offrom- .55 to .85% carbon, from 1.1 to 1.55% manganese,- from .25 to .40%silicon, from .85 to 1.35% chromium, from. .08 to .20.% vanadium and thebalance substantially iron, said rail, in the hot-rolled condition aftercooling toatrnospheric temperature from the final rolling temperature,being highly. resistant to shelling under repeated heavy. impact andexhibiting an average Brinell hardness number of from 310 to 360 withoutheat treatment.

2. A railroad rail of fine-grained alloy steel consisting essentiallyof'about .7% carbon, about 1.3% manganese, about 30% silicon, about1.00% chromium, about .11% vanadium and the balance substantially iron,said rail, in the hot-rolled condition after cooling to atmospherictemperature from the final rolling temperature, being highly resistantto shelling under repeated heavy impact and exhibiting an averageBrinell hardness number of from 310 to 360 without heat treatment.

References Cited inthe file of thispatent,

Alloys of Iron and: Chromium, .Low- Chromium, vol. 1, page 223. Editedby. Kinzel and Crafts. Published by the McGraW-HillBook Co., New York.

The Journal of the Iron and Steel Institute, vol. 2, of 1914, page 372.

1. A RAILROAD RAIL OF FINE-GRAINED ALLOY STEEL CONSISTING ESSENTIALLY OFFROM .55 TO .85% CARBON, FROM 1.1 TO 1.55% MANGANESE, FROM .25 TO .40%SILICON, FROM .85 TO 1.35% CHROMIUM FROM .08 TO .20% VANADIUM AND THEBALANCE SUBSTANTIALLY IRON, SAID RAIL, IN THE HOT-ROLLED CONDITION AFTERCOOLING TO ATMOSPHERIC TEMPERATURE FROM THE FINAL ROLLING TEMPERATURE,BEING HIGHLY RESISTANT TO SHELLING UNDER REPEATED HEAVY IMPACT ANDEXHIBITING AN AVERAGE BRINELL HARDNESS NUMBER OF FROM 310 TO 360 WITHOUTHEAT TREATMENT.